The present invention relates to an optical storage apparatus for optically recording and reproducing information to/from an exchangeable medium such as an MO cartridge or the like. More particularly, the invention relates to an optical storage apparatus for electrically substituting a lens position sensor which is eliminated to make the apparatus thin.
Attention is paid to an optical disk as a storage medium as a center of multimedia which has rapidly been developing in recent years. For example, as for an MO cartridge of 3.5 inches, MO cartridges of 128 MB, 230 MB, and the like are provided. An optical disk drive using such an MO cartridge is provided as an external storage apparatus of a desk-top type personal computer. Further, it is also strongly desired to use the optical disk drive in a notebook-sized personal computer having an excellent portability which has rapidly been spread in recent years. In order to equip the optical disk drive as an external storage apparatus as standard equipment, it is necessary to miniaturize and thin the optical disk drive. For example, a thickness of an HDD or FDD which is presently installed in a desk-top type personal computer is equal to about 17 mm. It is also necessary to make an optical disk drive thin to a similar extent.
The optical disk drive has a pickup mechanism of a linear driving type in the direction which traverses tracks on a medium. The pickup mechanism is constructed of a fixed optical unit and a movable optical unit mounted on a carriage which is linearly driven by a VCM. The movable optical unit is equipped with a lens actuator and has a relatively complicated mechanism in which a two-dimensional degree of freedom for moving an objective lens in the direction traversing the tracks by a current supply to a tracking coil and for moving the objective lens in the vertical direction by a current supply to a focusing coil is required. Further, a lens position sensor is usually mounted on the lens actuator. The lens position sensor can move the objective lens to the inner side or the outer side by only a micro distance around a position where the center of the objective lens is made coincide with the optical axis of a light beam from the fixed optical unit as a center by the current supply to the tracking coil. The lens position sensor detects a deviation amount of the optical axis of the lens from a neutral position of the lens. Consequently, in order to make the optical disk drive thin, it is necessary to simplify a structure of a pickup and to reduce a space in the height direction. If the lens position sensor provided for the lens actuator can be omitted, the optical disk drive can be made thinner.